Adcom Gfa 565 Amplifier Service Manual

[bainesni]

I have recently acquired a pair of "Dead" Adcom GFA 565 Mono Blocks. Previous owners have removed various parts from the control boards, and I am unable to figure out what the original fault or faults were. I have reached the stage were I require a circuit diagram, or a copy of the service manual to make any further progress. The overall condition of the equipment is not bad, and they definitely look resurrectable. Anyone out there Know where I can get an email copy of the service manual?
I would really appreciate any leads.
Nick.

[anatech]

Hi Nick,
Nice ! These are good amps.

-Chris

[djk]

http://www.diyaudio.com/forums/attac...amp=1033478920

http://www.diyaudio.com/forums/attac...amp=1033478982

Adcom 2A (servo IC) is AD 820

[anatech]

Hi Nick,
The first thing you should do is remove the "control PCB". Remove the trim pot and electrolytic caps, also the IC if it's there. Now, immerse the board into a bath of "Simple Green" or similar (aqueous degreaser) and clean the board very thoroughly. I use an ultrasonic cleaner and highly recommend that you do the same. If you think it's clean, run it through again. Discard the fluid, do not reuse it on anything else. Water rinse and blow dry with a hair dryer. Reassemble the board. You may need to replace the voltage regulators and the IC. Reinstall the trim pot and a set of brand new capacitors. The other ones were already thrown out, right?

Some of the original caps leak an invisible fluid that is extremely hard to remove. It's corrosive and conductive. This is probably why you were given these two. The fault is normally high DC offset.

-Chris

[bainesni]

Well I managed to get hold of a service manual, and now I have more questions than answers!
Chris you are on the money. I noticed that the two mounting screws at the top of the control board are corroded. They are right next to the caps you mentioned. The IC is still on the board, but the solder side of the board gives me the impression that it got really hot! I can see that this is not going to be a quick fix!
I checked the soft start circuit, and the 4,7 ohm resistor is fine.
The banks of power transistors also check out OK. It is quite possible that the original shutdown was that of offset error.
I will report back as and when I make more progress.
I am still looking for a decent circuit diagram. I did follow up the suggested leads, but the copy that I downloaded wasn't clear enough to see anything meaningful.
Thanx guys for the help to date.
Nick

[anatech]

Hi Nick,
I've yet to find a clear copy on the net, so you aren't alone.

-Chris

[trayton]

Hello,

I've managed to take my hands on a GFA565 with minor issues according to the previous owner. He already checked the amp with a technician who listed what parts should be replaced which mainly located on the control board. However, there is a part which can not be identified since it's heavily burnt.
I see that djk has already posted the schematic but the resolution is pretty low. Could anyone help me by sending me the service manual in good quality?

[pupnik]

This guy has taken some detailed pics of his GFA-565. Maybe they will help you identify components.

http://www.flickr.com/photos/4949382...7594576021976/

Cheers

[trayton]

Thank you popnik! Meanwhile I have bought the service manual, so I'm already busy buying the neccesary parts.